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Reflection for C++26

(isocpp.org)
196 points svlasov | 2 comments | 30 Jun 24 11:26 UTC | HN request time: 0.417s | source
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lallysingh ◴[01 Jul 24 23:00 UTC] No.40851756[source]▶
Wow this got really long. I was one of the coauthors for a reflection proposal (N3340) over a dozen years ago. Implementing compile-time reflection is honestly trivial - you basically transfer data from the symbol table on-demand into template specializations. It was roughly 1500 LOC to modify g++ to do it.

Looking at the examples (https://isocpp.org/files/papers/P2996R4.html#examples) what really stands out is the direct integration of type-syntax into the language. It fits in with a certain token-substitution way that connects back to templates. It also replaces some of the uglier operators (typeof?).

I hope it goes int! During the language's stagnation I left for a while, perhaps it'll be competitive again soon.

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stiglitz ◴[01 Jul 24 23:36 UTC] No.40851990[source]▶
By ”stagnation” do you mean “not getting new features”?
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jacoblambda ◴[02 Jul 24 00:48 UTC] No.40852476[source]▶
C++ has gotten a ton of quality of life features with each update. The issue is less that new features aren't coming and more that new features bake through countless iterations of proposals for close to or often over a decade until everyone in WG21 is happy.

So it's not that we aren't getting features. They are coming quite fast and people regularly complain that new C++ has too many things for them to learn and keep up with. The issue is that those are the same features everyone has been asking for for over a decade so the people that really care found workarounds and eventually move over to the new std way of doing things when they can while everyone else continues waiting for that one feature they really care about.

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physicsguy ◴[02 Jul 24 06:50 UTC] No.40854139[source]▶
> the people that really care found workarounds

Or stopped writing C++, I'd consider myself one of these for many use cases I used to use it for.

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chipdart ◴[02 Jul 24 10:34 UTC] No.40855243[source]▶
> Or stopped writing C++, I'd consider myself one of these for many use cases I used to use it for.

Some use cases like GUI programming sound like they are better addressed by specialized tech stacks. Nevertheless, either you're talking about greenfield projects or you are hard pressed to find a justification to rewrite a project in another framework. Claiming you stopped writing C++ doesn't fit the bulk of the experience of anyone maintaining C++ projects.

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1. PathOfEclipse ◴[02 Jul 24 13:49 UTC] No.40856651[source]▶
My experience maintaining old codebases is that you are just as hard-pressed to find a justification to write code to use new language features, or even to take the time to upgrade the language and compiler version. Most often you just continue writing code in the same style as the rest of the code base using an old version of the language and runtime.
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2. chipdart ◴[02 Jul 24 17:38 UTC] No.40858814[source]▶
> My experience maintaining old codebases is that you are just as hard-pressed to find a justification to write code to use new language features, or even to take the time to upgrade the language and compiler version.

That's perfectly fine. You should only pay for what you use.

Your average project, however, consumes dependencies and needs to keep them updated. Just because the code you write doesn't use them that doesn't mean your dependencies don't. So everyone still benefits with each release of C++ even if the are not using fancy features.